I'm certainly not an expert on this, but aren't there issues with corpses of urination, defecation and even potentially ejaculation, not to mention vocalizations as gases escape? Twelve hours would seem like enough time for these to be concerns.
Do live people not fart?
12 hours, covered up, low humidity in the cabin - the stiff will last for a good few hours I reckon. Can't see it bloating up for a good while.